1. Field of the Invention
The present invention relates to a liquid jet recording head for use in a liquid jet recording apparatus of an ink jet system for discharging the recording liquid (ink) as liquid droplets from the discharge ports (orifices), and a manufacturing method thereof, as well as a liquid jet recording apparatus with said liquid jet recording head mounted thereon.
2. Related Background Art
The liquid jet recording apparatuses of ink jet systems are very sensitive to disturbance, while features such as sufficiently high frequencies of producing droplets, ease of achieving the higher speed, higher precision, and multi-color printing are greatly expected in the future.
A liquid jet recording head of such a liquid jet recording apparatus comprises a substrate having discharge energy generating elements, and a nozzle layer (liquid flow passage forming layer) for forming liquid flow passages or a liquid chamber in communication to discharge ports (orifices) thereon, said substrate being typically subjected to thermal oxidation of the surface of a Si substrate of single crystal, and then formed with discharge energy generating elements such as electrothermal converting elements by well-known photolithography, its surface covered with an electrically insulating layer made of SiO.sub.2, SiC, or Si.sub.3 N.sub.4, and a protective layer such as a Ta film for preventing damage (cavitation erosion) to discharge energy generating elements caused by mechanical impact in discharging the recording liquid, with a Ta.sub.2 O.sub.5 film provided to reinforce the intimate contact between the electrically insulating layer and the Ta film, if necessary. Also, a glass ceiling plate with an inlet opening for supplying the recording liquid such as ink to the nozzle layer is laid on the nozzle layer, said ceiling plate being bonded to the nozzle layer by adhesive.
The manufacturing methods for the liquid jet recording head with the above constitution can be classified into the four types as follows.
(1) Patterning a glass ceiling plate bonded with a dry film, and joining it to a substrate (see Japanese Laid-Open Patent Application No. 56-123869).
(2) Molding a nozzle layer made of resin by injection molding, and joint it to a substrate (see Japanese Laid-Open Patent Application No. 3-101954).
(3) Providing a resist pattern on a substrate, applying a resin film thereto, joining a ceiling plate thereto, curing the resin film, and then dissolving away the resist (see Japanese Laid-Open Patent Application No. 62-253457).
(4) Subjecting the surface of a second substrate which is comprised of a Si substrate of single crystal, as parent material, like a first substrate (heater board) having discharge energy generating elements, to anisotropic etching, to create V-character grooves, and bonding this substrate as a nozzle layer to the first substrate. Processing the surface of the second substrate constituting the nozzle layer to be a (100) plane, and forming the grooves of V-character in cross section by anisotropic etching at an etching rate for (111) plane of substantially zero (see Japanese Laid-Open Patent Application No. 54-150127).
In recent years, the liquid jet recording apparatus has advanced for the faster speed, greater precision, and higher image quality, and therefore, the development of liquid jet recording heads with ease of fabrication for the higher density of liquid flow passages, and the capability of higher discharge frequency, is desired. Also, one way of printing on plain paper is to use a strong base ink with the addition of urea. In this case, it is also necessary to improve the ink resistance property of structural members constituting the liquid flow passages in the liquid jet recording head, and the chamber.
However, according to the above-mentioned conventional arts, the liquid jet recording heads fabricated by the methods of (1) to (3), as previously described, all have the nozzle layer formed of resin, and are significantly limited in the materials from the viewpoint of the ink resistance property. Also, to promote the higher density of liquid flow passages, each liquid flow passage is required to have a high aspect ratio, i.e., a narrow width and greater height in cross section, but with the methods of (1) and (2), which use photosensitive resin, it is difficult to produce a high aspect ratio, and with the method of (3), which adopts the injection molding, it is also difficult to attain a sufficient shape precision if the liquid flow passages have a high aspect ratio.
To provide the liquid jet recording head operable at high frequencies for discharging, the cross-sectional dimensions of each liquid flow passage are required to be large, and to avoid the larger dimensions of the liquid jet recording head, the liquid flow passages are also required to have a high aspect ratio.
A method of (4) is superior in the ink resistance property, satisfactory in heat resistance, and simple in the manufacturing process, because the second substrate for the nozzle layer is the same Si material as the first substrate for the heater board, further with the advantages of having uniform ink wettability and stable discharge performance, owing to the orifice face to which discharge orifices are opened being constructed by the end faces of both Si substrates. However, since the grooves formed by anisotropic etching as above described do not allow the aspect ratio to be changed, and the second substrate has its bottom surface having the V-character shaped grooves facing down toward the heater board and joined thereto, the liquid flow passages with higher density will reduce the unetched width, resulting in unsolved problems of producing a lot of defectives.